General Physics Colloquium, Professor Katja Nowack, Cornell University

Title:  Understanding electronic transport through local magnetic measurements

Abstract:  Electric charge can flow in unexpected ways through a sample, in particular in dissipationless conductors. In this talk, I will discuss how we use a local magnetic probe to visualize electronic transport in two different types of dissipationless conductors. First, we study microstructures fabricated from a heavy-fermion superconductor that exhibit an unusual resistive superconducting transition. We show that this behavior is explained by a spatially modulated transition temperature, and we discover that local strain is the cause of the spatial modulation. Second, we visualize how a non-equilibrium current flows in a quantum anomalous Hall insulator by imaging the magnetic field produced by the current. Against the prevalent expectation that the transport current is concentrated along the edges, we find that the current can flow in the interior of the sample within the dissipationless regime.